Process of preparing nylon yarn



.either direction. and is due to the nature of the construction offabric United States Patent PROCESS 0F PREPARING NYLON YARN AaronBurleson, Burlington, N. (3., assignor, by mesne assignments, toPatentex, Inc., New York, N. Y., a corporation of New York No Drawing.Application July 13, 1953, Serial No. 367,776

2 Claims. (Cl. 57-157) The present invention relates to knitted fabricsand, more particularly, to knitted nylon fabrics, especially hosieryfabrics, possessing increased elasticity.

The elasticity of a knitted fabric is dependent on severalcharacteristics of the fibre or fibres Comprising the same and thefabric itself, namely, strength of fibre, longitudinal'elasticity offibre, angular or bending elasticity of fibre, the number and shape ofloops or stitches in the fabric and position of loop in the fabric.Normally, a knitted hosiery fabric contains well rounded stitches orloops which lie flat in the fabric and, as a result of the loopformation, the fabric is limited in its stretch characteristics. Forexample, the stretch of full fashioned nylon hosiery runs approximately70% in This stretch is known as fabric stretch in that the loops becomedeformed when stress is applied. With nylon, or other yarn of goodresiliency, the

loops return to their normal shape when the stress applied to stretchthe fabric is released.

Greater fabric stretch than 70% can be attained in nylon fabric ifsufiicient stress is applied thereto. However, under this condition, theyarn in the fabric is itself stretched excessively and the stressnecessary to accomplish this is uncomfortable under actual wearcondition. Furthermore, repeated stretching under such conditionsnecessarily induces a loss of shape in the knitted fabric. Thesedifficulties are particularly apparent in ladies nylon hosiery whereconsiderable strain is imposed on the fabric about the knee area.

It will be apparent from the foregoing that the production of knittednylon fabric, particularly hosiery fabric, possessing increasedelasticity, is highly desirable and the principal object of the presentinventionis to provide such knitted nylon fabric of increasedelasticity.

Another object of the invention is the provision of knitted fabric whichoffers increased comfort in wear under stress conditions and in generalpossesses an improved overall appearance.

A further and more specific object of the invention is to provide aknitted nylon hosiery fabric which, by virtue of its increasedelasticity, possesses a greater latitude of wear and covers a widerrange of leg and foot sizes.

Still another object of the invention is the provision of novelprocedures for producing knitted nylon fabrics possessing increasedelasticity and comfort in wear and improved appearance.

Other and more specific objects will appear hereinafter.

The improved knitted fabric is obtained, according to the presentinvention, by a process which includes the steps of first presettingnylon yarn, twisting a part of the yarn in one direction to impart aright twist torque thereto and twisting another part of the yarn in theopposite direction to impart a left twist torque thereto, sizing saidtwisted yarn to .hold the torque therein dor- 2,772,191 C6 Patented Nov.27, 1956 mant temporarily while knitting, forming a fabric from thetwisted yarn by alternately knitting at least one course first with theyarn which has been twisted in one direction and then with the yarnwhich has been twisted'in the other direction and, thereafter, removingthe size from said fabric to release the torque in said twisted yarn.

In contrast to conventional knitted hosiery fabrics which possess apattern of uniform loops 'or stitches that lie in a plane or flatsurface, the loops or stitches in the fabric of the invention turn overon edge when "the size is removed, due to the torque in the yarn, andthus the face of the fabric shows a series of loop edges rather thanopen stitches. The torque of the yarn also causes a fabric torque, sothat the chains of loops or wales move in a diagonal direction toregular or normal fabric. In other words, the loops in the fabric take adifferent position than in conventional knitted fabrics, due to theforce of the torque and, as a result, more loops or stitchesautomatically form in a given area. Thus, for example, where a normalknitted fabric may finish five inches long, a fabric of the inventioncould reasonably finish only two and one-half inches long. However, thelatter fabric has the ability to stretch up to 250%, whereas the stretchof the normal fabric is about 70%, as noted above.

In view of the torque created in the fabric, wherein loops form in adiagonal direction to normal stitches, it is essential to alternateoppositely twisted yarn, i. e., yarn with right and lefttwist torque, inthe courses forming the fabric. For example, forty-eight courses can beknitted with yarn having left twist torque and then alternated withforty-eight courses of yarn of right twist torque. Alternately, thefabric may be knitted one and one, or two and two, i. e., by knittingone or two courses, respectively, with'yarn twisted in one direction andthen knitting one or two courses with yarn twisted in the oppositedirection. In short, the number of courses knitted with each yarn can bevaried at will, e. g., from at least one to 400 and even higher, anddepends primarily on the nature and ultimate use of the fabric. In allcases, however, the fabric produced according to the invention, usingoppositely twisted nylon yarn, possesses a herringbone pattern which ismore pronounced the larger the number of courses alternately knit withoppositely twisted yarn and which improves the stretch characteristics,appearance and comfort in wear.

According to the process of the invention, the nylon yarn must beinitially preset, otherwise the twisted yarn does not produce theangularity of stitch direction which gives the desired results. Nylonyarn is thermoplastic and by presetting the same, i. e., by treating theyarn in high wet heat, before twist insertion, the individual filamentsare shaped or set in parallelism with each other. Accordingly, whentwist is inserted, a permanent torque takes place in the yarn which hassufficient force to create diagonal stresses, due to the tendency of theyarn to seek its original shape of filament parallelism. The presettingoperation also serves to prevent further shrinkage of the yarn insubsequent operations and avoids the possibility of permanently settingthe twist in the yarn, and thereby eliminating the torque necessary togive the de sired results, in the event the yarn is exposed to furtherheat treatment after it has been twisted.

The initial'presetting operation, according to the present invention, iscarried out in the absence of appreciable twist.

The conditions for presetting the nylon yarn with wet heat, i. e., steamor hot water, will be readily appreciated by those skilled in the art.Normally, this operation may be efiected by exposing the yarn to steamhaving a temperature within the range of 220 F. to 270 F. for a 3 periodof the time between 15 and 60 minutes, or hot water at a temperaturebetween 190 F. to 212 F. for between and 60 minutes, although theseconditions can be varied, depending upon other operating features. 7

In a typical presetting operation, the yarn is first wound onto abobbin, tube or cylinder made up of a material thatwill withstand thepresetting temperature. The resulting package of nylon yarn is thenplaced in an appropriate retort and subjected to treatment with steam ata pressure of 25 poundsper square inch (gauge) for at least minutes togive a satisfactorily preset yarn. Substantially similar results canbeobtained by treating the yarn is skein or cake formation with steamand/ or hot water, although presetting the ferred.

After the presetting operation, the yarn is twisted sufficiently toinsert therein the torque necessary to produce the desired fabric. "Theamount of twist inserted in the yarn can be widely varied and dependsprimarily on the size of the yarn being treated and the use to which thefabric will be put. Generally speaking, however, when using nylon yarnvarying from denier to 100 denier, a twist of from 32 turns to 9.5 turnsper inch will give satisfactory fabrics. For example, a highly desirablefabric is obtained by alternately knitting equal multiples of courseswith oppositely twisted'40 denier nylon yarns containing 15 to 20 turnsper inch.

yarn on package is pre-' The twist imparted to the yarn should be of thesame degree in both directions if the number of courses in the bands areto be equal. Otherwise, if the number of courses in bands are unequal toform a difierent pattern fabric, difierent twist factors in right andleft directions are necessary to balance the fabric.

After the desired twist has been inserted in the yarn, a coating orsizing is applied thereto preliminary to the knitting of the desiredfabric. The sizing binds the filaments of the yarn together, deadens theliveliness thereof and restricts the action of the torque impartedthereto sufficiently to avoid kinking in the knitting operation. Afterthe fabric has been knit, the size is removed in any conventionalmanner, e. g., by scouring, and the fabric which, up to this point, hasthe appearance of conventional knitted fabric, assumes a herringbonepattern, due to therelease of the torque'in the yarn.

Any of the sizes normally used in knitted and other textile operationscan be used for the purpose of sizing the yarn according to the processof the invention. However, particularly desirable for use in the presentinvention is the polyvinyl alcohol size known in the trade as PM 90.

As will beappreciated, the quantity of size utilized treatment uponremoval of the size. For example, knitted hosiery prepared according tothe invention may be dyed, finished, extracted and/or boarded. v

The invention, as described above, is further illustrated by thefollowing examples.

Example 1 Forty denier raw nylon yarn is drawn from pirnpackages andwound into skeins. These skeins are then placed in a retort andsubjected r030 pounds of steam pressure at a temperature of 275 F. for aperiod of approximately 30 minutes. This treatment preshrinks andpresets yarn permanently, provided higher temperatures are not used insubsequent operationsf After a short lagging period,

applied to yarn'intwo operations of sizing, applying 3% a in eachoperation. The yarn is sized by the common method of passing yarn oversize .dip roll onto large take-up package. After each sizing operation,the yarn is lagged for 16 hours in an atmosphere of relative humidity ata temperature of 84 F. and force-dried in oven for 3 hours at atemperature of 160 F. Following the last dryingiperiod, the yarn islagged for 4 hours in a relative humidity of 62% at 78 F. to allow yarnto reach an equilibrium of a moisture regain of approximately 4%. Theyarn is then'transferred onto a coming package and in this operation, 4%oil is applied by passing over,oil roll. I 1 g In the knittingoperation, the yarn is-set up on machine under two carrier systems, onecone package ofyarn having right twist torque and the other cone packageleft twist torque. In the welt area, the yarn is knit alternately 48courses right twist torque and 48 courses left twist torque. The fabricin this state appears very similar to ordinary knit fabric, due to thesize holding torque in yarn dormant. When the fabric is subjectedtosteam or hot water, the size breaks down and torqueiof' yarn comesinto action contracting fabric 100% or more. The torque causes loops toturn over. on edge and move in a diagonal direction as compared toperpendicular can be widely varied, theoptimum amount thereof de- 7pending upon other. operational details, e. g., nature of the size oryarn, or amount of twist. Broadly speaking, however, enough size shouldbe utilized to retain the right or left twist'torque in the yarn andusually from 5% to 7% solid size or Weight of yarn is sufiicient.

It will be understood that the nylon yarns, preset,-

twistedand sized, as above described, can be knitted in any suitable wayinto the desired fabrics. For example, the yarns can be knit on circularor flat knitting machines to give seamless or full-fashioned hosiery. Aparticularly advantageous product is obtained by replacing the welt ofotherwise conventional knitted hosiery with a welt constructioncomprising alternate series of courses of oppositely twisted nylon yarn,according to the present invention. A Welt of this nature has been foundto possess substantially increased elasticity which relieves the strainon the hosiery under stress conditions, for example, when the wearersknee is flexed or when the wearer is in a sitting position, and permitsthe hosiery to return to its original shape without bagging when thewearer changes from a sitting to a standing position.

It will also be understood that the knitted fabric of the invention maybe exposed to any conventional afterdirection in normal knitted fabric.n H

Example II Forty denier raw nylon yarn is drawn from pirns ontocylinders, bobbins or some constricting package under low tension.-These packages of yarn are then placed in a retort and are subjected to30 pounds of steam pressure at a temperatureof 275 F. for a period ofapproximately 30 minutes. The treatment presets yarn permanently,providedhigher temperatures are not used in subsequent operations.Thereafter, the procedure described in Example 1, involving twisting,sizing and knitting, is carried out to'give a product similar to that ofExample I, possessing highly desirable elasticity characteristics.

While the invention is of particular advantage inconnection with theproduction of hosiery fabrics, it will be appreciated that the inventionis broadly applicable to-the production of any type of knitted nylonfabrics where increased elasticity or fabric stretch is a desirablecharacteristic. Likewise, it is to be understood that the term ,nylon,as used herein, refers to the well-known synspirit and scope thereof, itis to be understood that this invention is not to be limited to thespecific embodiments thereof, except as defined in the appended claims.

This application is a continuation-in-part of my copending applicationSerial No. 342,709, filed March 16, 1953.

I claim:

1. A process of preparing a markedly lively but uncrimped and uncoiledcontinuous filament nylon yarn which comprises presetting andsubsequently twisting a nylon yarn to impart substantial liveliness andtwist torque to said yarn, thereafter sizing said lively, twist torqueyarn to subdue temporarily the said liveliness and restrict the actionof the torque imparted thereto sufiiciently to enable satisfactoryknitting of said yarn to produce a stretchable fabric.

2. The process of claim 1, in which the said lively twist torque yarn issized with a polyvinyl alcohol size in an amount sufficient to retainthe twist torque in said yarn.

References Cited in the file of this patent UNITED STATES PATENTS BengerMay 1, 1900 Harron et al. Apr. 7, 1931 Carmer Feb. 21, 1933 KugelmanOct. 5, 1937 Hemmerich Nov. 2, 1937 Meyers Dec. 21, 1937 McNamee July19, 1938 Miles Sept. 15, 1942 Hathorne Nov. 12, 1946 Armstrong Feb. 18,1947 Bell Apr. 17, 1951 Reinstein Jan. 29, 1952 Neumager June 16, 1953Beard Feb. 23, 1954

1. A PROCESS OF PREPARING A MARKEDLY LIVELY BUT UNCRIMPED AND UNCOILEDCONTINUOUS FILAMENT NYLON YARN WHICH COMPRISES PRESETTING ANDSUBSEQUENTLY TWISTING A NYLON YARN TO IMPART SUBSTANTIAL LIVELINESS ANDTWIST TORQUE TO SAID YARN, THEREAFTER SIZING SAID LIVELY, TWIST TORQUEYARN TO SUBDUE TEMPORARILY THE SAID LIVELINESS AND RESTRICT THE ACTIONOF THE TORQUE IMPARTED THERETO SUFFICIENTLY TO ENABLE SATISFACTORYKNITTING OF SAID YARN TO PRODUCE A STRETCHABLE FABRIC.